Answer:
m = 50 [kg]
Step-by-step explanation:
The potential energy can be calculated by means of the following equation.

where:
Ep = potential energy = 735 [J]
m = mass [kg]
g = gravity acceleration = 9.81 [m/s²]
h = elevation = 1.5 [m]
Now replacing:
![735=m*9.81*1.5\\m = 50 [kg]](https://img.qammunity.org/2021/formulas/physics/college/by42cz46oovqdl8ak64k7vhl2b0l54ebjp.png)